Stabilizer for single powder photographic developer



United States Pat t 2 Claims. (31. 96-66) The present invention relates to single powder photographic developers, and more particularly to compositions containing organic stabilizers for eifectively preventing reaction between the developing agent and the alkaline ingredients of such compositions.

The advantages of single powder photographic developers are readily recognized in that such powders may be blended in one operation and packaged in a simple, singlecomponent container. Such powders contain the usual Patented Dec. 1 1959 presence of benzotriazole and, hence, this component may b'e'used in the compositions hereof, either as a restraineror to produce blue-black tones. .Itis also recommended that-a sequestering agent be added to take care'of salts present in hard water and, to this end, ethylene diamine tetra acetic acid may be effectively employed.

The following examples will serve to illustrate the invention, but it is to be understood that the invention is components for photographic developers such as the developing agents, anti-oxidant or preservative, alkali energizer and an anti-fogging agent. It has been found, however, that when these components are blended in the form of a dry powder there is a marked tendency for the organic developing agent to react with the alkali, causing deterioration of the photographic properties of the composition. It is, therefore, necessary to incorporate in the powder a substance which will preclude such reaction and operate to stabilize the developer.

Recognition of this fact has led the art to select as stabilizers, such substances as benzoic, maleic, boric and phthalic anhydrides and metaboric, salicylic and phthalic acids. Optimum results, however, are not secured by utilization of any of these components. Thus, many are only moderately effective and display properties which lead to additional problems. For example, they cannot be employed with any degree of success where anhydrous sodium carbonate is employed as the alkali. Similarly, they are of little use should it be desired to employ benzotriazole as a blue-black toner or as a restrainer. Again, they dissolve relatively slowly in water, thereby greatly prolonging the mixing operation designed to produce the active developing solutions. Finally, these acidic substances have a tendency to react with sulfite and carbonate, thereby forming gases which may build up objectionable pressures in hermetically sealed containers.

It has now been discovered that the disadvantages of the previously suggested stabilizers may be overcome while obtaining single powder developers, readily soluble in water with little tendency to gas formation during storage, by employing anhydrous oxalic acid as the stabilizer. Single powder developers containing anhydrous oxalic acid as a stabilizer constitute the purposes and objects of the present invention.

The single powder developers contemplated herein contain the usual developer components, such as the developing agent, i.e., metol, phenidone, hydroquinone, p-aminophenol, hydrochloride, pyrogallol and the like; a preservative or anti-oxidant such as an alkali metal sulfite, i.e.,

potassium sulfite, potassium metabisulfite and the like; an

not restricted thereto. The components ofthe various examples may be packaged as single powder mixtures for dissolution in one liter of water to prepare the-developer solution.

Example I i v i" Grams Ethylene diamine tetra acetic acid- Q 0.8 Borax I 4.0 Oxalic acid, anhydrous 0.6 Sodium sulfite 80.0 Metol 1.5 Hydroquinone 3.0 Potassium bromide 0.5

Example II Grams Ethylene diamine tetra acetic acid 0.5 Sodium sulfite 44.0 Oxalic acid, anhydrous 0.6 Diamino phenol hydrochloride 6.6 Potassium bromide 0.55

Example III Grams Ethylene diamine tetra acetic acid 0.8 Sodium carbonate, monohydrate 25.0 Oxalic acid, anhydrous 1.0 Potassium metabisulfite 2.5 Sodium sulfite 13.0

Metol 1.3 Hydroquinone 3 .7 Benzotriazole 0.006 Potassium bromide 0.3

Example IV Grams Ethylene diamine tetra acetic acid 0.8 Sodium carbonate, monohydrate 27.0 Oxalic acid, anhydrous 1.0 Potassium metabisulfite 2.5 Sodium sulfite 10.0 Phenidone 0.10 Hydroquinone 6.0 Benzotriazole 0.006 Potassium bromide 0.3

Example V Grams Ethylenediamine tetra acetic acid 1.0 Sodium carbonate, anhydrous 23.0 Oxalic acid, anhydrous 1.0 Potassium metabisulfite 2.5 Sodium sulfite 10.0 Phenidone 0.10 Hydroquinone 6.0 Benzotriazole 0.006 Potassium bromide 0.3

Example VI Grams Ethylene diamine tetra acetic acid 1.0 Sodium carbonate, monohydrate 75.0 Oxalic acid, anhydrous 3.0 Sodium sulfite 55.0 Potassium bromide 10.0 Hydroquinone 35.0

Developers constituted according to the examples,

after storage for prolonged periods at 120 F showed no significant decomposition and evidenced no gas formation when placed in hermetically sealed cans. However, omission of the oxalic acid caused the mixtures of the examples to become'badly discolored after one days storage with a marked deterioration in their photographic activity.

All of the compositions of the examples dissolved readily in water to form developing solutions photographically equal to those freshly prepared from the individual chemical constituents. 3

I claim: v .1. A stabilized single powder developing composition consisting essentially of an organic silver halide developer selected from the group consisting of methyl-p-amino phenol sulfate, 1-phenyl-3-pyrazolidone, hydroquinone, paminophenol hydrochloride, pyrogallol and mixtures thereof, an alkali selected from the group consisting of alkali carbonates, sulfites, borates and mixtures thereof, a stabilizing'agent consisting essentially of anhydrous oxalic acid, an'antifogging' agent and ethylene diamine tetracetic' acid.

2. A stabilized single powder developing composition 4 consisting essentially of an organic silver halide developer selected from the group consisting of methyl-p-aminophenol sulfate, 1-phenyl-3-pyrazolidone, hydroquinone, paminophenyl hydrochloride, pyrogallol and mixture thereof, an alkali selected from. the group consisting of alkali carbonates, sulfites, borates and mixtures thereof, ethylene diamine tetra acetic acid, benzotriazole, an antifoggant and a stabilizing agent consisting essentially of anhydrous oxalic acid.

References Cited in the file of this patent UNITED STATES PATENTS 2,162,765 Tarnofi June 20, 1939 2,649,376 Rasch et al Aug. 18, 1953 .FOREIGN PATENTS 16,537 Great Britain Aug. 3, 1889 of 1888 I 725,892 Great Britain Mar. 9, 1955 OTHER REFERENCES Chemistry of Carbon Compounds, Rodd, vol. I, part B (1952), page 955. (Copy in Div. 38.) v 

1. A STABILIZED SINGLE POWER DEVELOPING COMPOSITION CONSISTING ESSENTIALLY OF AN ORGANIC SILVER HALIDE DEVELOPER SELECTED FROM THE GROUP CONSISTING OF METHYL-P-AMINO PHENOL SULFATE, 1-PHENYL-3-PYRAZOLIDONE, HYDROQUINONE, PAMINOPHENOL HYDROCHLORIDE, PYROGALLOL AND MIXTURES THEREOF, AN ALKALI SELECTED FROM THE GROUP CONSISTING OF ALKALI CARBONATE, SULFITES, BORATES, AND MIXTURE THEREOF, A STABILIZING AGENT CONSISTING ESSENTIALLY OF ANHYDROUS OXALIC ACID, AN ANTIFOGGING AGENT AND ETHYLENE DIAMINE TETRACETIC ACID. 